An atom is made from a nucleus surrounded by electrons. The nucleus contains protons and neutrons. Isotopes are atoms that have the same number of protons, but different numbers of neutrons.
An early model of the atom was the plum pudding model. It was disproved by Rutherford's scattering experiment and replaced by the nuclear model.
You should be able to describe the nuclear modelnuclear model: The scientific idea that an atom has electrons surrounding a nucleus that contains protons and neutrons. of the atom [atom: All elements are made of atoms. An atom consists of a nucleus containing protons and neutrons, surrounded by electrons. ].
Atoms contain three sub-atomic particles called protonsproton: A proton is a small particle with a positive charge found in the nucleus of the atom., neutrons and electrons [electron: An electron is a very small negatively-charged particle found in an atom in the space surrounding the nucleus. ]. The protons and neutrons are found in the nucleus at the centre of the atom. The nucleus is very much smaller than the atom as a whole. The electrons are arranged in energy levels around the nucleus.
The table shows the properties of these three sub-atomic particles.
|Particle||Relative mass||Relative charge|
The number of electrons in an atom is always the same as the number of protons, so atoms are electrically neutral overall. Atoms can lose or gain electrons. When they do, they form charged particles called ions:
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.